cache this

app/models/conversation.rb

@@ -105,6 +105,9 @@ class Conversation < ApplicationRecord
   belongs_to :contact_inbox
   belongs_to :team, optional: true
   belongs_to :campaign, optional: true
+  belongs_to :cached_last_message, class_name: 'Message', optional: true, foreign_key: 'last_message_id'
+  belongs_to :cached_last_incoming_message, class_name: 'Message', optional: true, foreign_key: 'last_incoming_message_id'
+  belongs_to :cached_last_non_activity_message, class_name: 'Message', optional: true, foreign_key: 'last_non_activity_message_id'
 
   has_many :mentions, dependent: :destroy_async
   has_many :messages, dependent: :destroy_async, autosave: true

app/models/message.rb

@@ -133,6 +133,7 @@ class Message < ApplicationRecord
   has_many :notifications, as: :primary_actor, dependent: :destroy_async
 
   after_create_commit :execute_after_create_commit_callbacks
+  after_create_commit :update_conversation_cached_message_ids
 
   after_update_commit :dispatch_update_event
   after_commit :reindex_for_search, if: :should_index?, on: [:create, :update]
@@ -422,6 +423,15 @@ class Message < ApplicationRecord
   def reindex_for_search
     reindex(mode: :async)
   end
+
+  def update_conversation_cached_message_ids
+    updates = { last_message_id: id }
+    updates[:last_incoming_message_id] = id if incoming?
+    updates[:last_non_activity_message_id] = id unless activity?
+    # rubocop:disable Rails/SkipsModelValidations
+    conversation.update_columns(updates)
+    # rubocop:enable Rails/SkipsModelValidations
+  end
 end
 
 Message.prepend_mod_with('Message')